(a) All hoistways, except where exempt by the [Labor] Law in article 1, subdivisions 9, 10 and 11 of section 2, also article 11, section 270, shall be enclosed throughout their height by enclosures of fireproof materials. Every such enclosure shall be set flush with the hoistway line on all landing sides and shall have a roof of fireproof material, and if the enclosure extends to the top story it shall be continued to three feet above the roof, and shall have at the top a skylight in a metal frame at least three-fourths of the area of the shaft or exterior window with metal frame and sash.

(b) The bottom of the hoistway shall be of fireproof material unless the enclosure extends to the cellar bottom.

(c) All openings in such enclosure shall be provided with fire doors. (See § 8-2.18.)

(d) Where elevator shafts which are required to be enclosed are contiguous no wall is required between them; except that a partition or screen not less than six feet high shall be provided at the bottom of pit between adjacent shafts.

(e) Where the entrance to the elevator is on the street or outside of a building at the ground floor, the gate or door shall be not less than 66 inches high and shall extend to the floor level across its entire width.